1. Field of the Invention
This invention relates to a safety device for restraining a multiple part rim during the inflation of a truck tire, and particularly to such a device which is lightweight and portable, and suitable for field use.
2. Description of the Prior Art
Truck tires are commonly mounted on rims having two or more parts. During the mounting and inflation of truck tires on multiple part rims, it is possible that the lock ring and/or other parts of the rim, may become separated from the tire-rim assembly, causing the bead of the tire to become unseated from the rim and thus a sudden release of pressurized air from within the tire. This released air pressure can be extremely high and can cause the separated rim parts to be projected away from the assembly at considerable speeds. When this happens, the rim is said to "explode". In order to protect persons and property in the event of such a rim explosion, safety devices or cages are used to restrain the multiple part rim during the inflation of truck tires. These cages must be capable of withstanding the large forces produced by the impact of flying rim parts. As a result, most of the cages are heavy and not readily moved.
In many instances, however, it is desired to mount and inflate a truck tire in the field. For example, when a tire is repaired and must be inflated, such reinflations may occur on the highway or elsewhere away from the location of a tire cage. It is often difficult or impossible to move the heavy tire cages to a field location. As a result, it is usually necessary to take the rim and tire to an installation where the cage is available to inflate the tire.
Several portable light-weight safety cages have been manufactured by others for use in the field. One such cage, manufactured in Akron, Ohio by the Ken-Tool Division of Warren Tool Corporation, consists of two tubular-metal sections, each bent in a U-shape and joined to each other by a hinge member in the middle of the curved portions of their U-shapes. Flat metal strips are welded to the ends of the legs of each U-shaped member to form two continuous bands that encircle the tire. At the junctures of the strips with the legs, the bands are connected by collapsible braces, similar to those used in holding the collapsible legs of card tables extended. These braces are collapsed during storage of the cage, but during use they are extended to keep the leg-end portions of the U-shaped members spread from one another, while their curved portions are joined by the mentioned hinge member. During inflation of a tire on a multi-part rim, the hinged, curved portions of the U-shaped members wrap laterally across one portion of the tread, while the braced-apart flat strips of these members extend across a diametrically opposed portion of the tread, with the legs of the U-shaped members extending in chordal relation across the tire sidewalls and rim.
One problem with the foregoing safety cage is that the legs of the U-shaped members are easily bent outwardly by the force of a rim explosion, allowing the lock ring of the multi-part rim to escape from between them. Another problem is that collapsible brace members can be easily broken by the force of the explosion, allowing the rest of the tire and rim assembly to become dislodged from the cage.
Another type of portable cage, sold by Myers Tire Supply Company of Akron, Ohio, has a base made of two elongated tubular steel members, connected to each other in side-by-side relationship, and designed to support the tire and rim assembly on its side, with its central axis extending upwardly. The base also includes a shaft extending upwardly from a plate that is mounted on top of the two tubular steel members. When the tire and rim assembly is placed on the base, the shaft extends through the central opening in the rim. The cage also includes a retainer made of two elongated tubular steel members, connected to each other in side-by-side relationship by a centrally located plate that has an opening through which the shaft of the base extends. The tubular steel members of the retainer extend over the top of the tire and rim assembly, and the retainer is locked in place by a U-shaped clip that slides over the central plate and into a groove on the shaft of the base.
One problem with this cage is that because of the large central openings in multipiece rims, the tire and rim assembly can, during a rim explosion, shift laterally and then rotate upwardly around the outward edges of the tubular steel members of the retainer, thus becoming free of the cage. Making the tubular members of the retainer long enough to prevent this would unduly increase the weight and storeability of the cage, particularly for cages capable of holding the larger sizes of tire and rim assemblies.
Another problem with this cage is the tendency of the tubular members of the retainer to bend upwardly. This bending, combined with elongated flexing of the lock ring, can allow the lock ring to escape from the cage.
Still another problem with the latter cage resides in the ability of the tubular steel members of the retainer to become aligned with the tubular steel members of the base. With such an alignment, the more the base resists the forces of the explosion, the more this resistance is transmitted to the retainer, and vice-versa. Thus, there is a greater tendency for both the base and the retainer to deform and allow the lock ring to escape when these parts are aligned.